In general, the use of oscillatory flow to generate electricity is known. Exemplary references include U.S. Pat. No. 3,787,741 Gourlay and U.S. Pat. No. 4,029,979 Chapin.
The generator described by Gourlay comprises an acoustic oscillator and an acoustic resonant cavity. The generator is designed to operate at the resonant frequency of the cavity, the latter being formed in part by a piezoelectric disc which generates the electricity. Such designs depend on resonant operation. Consequently, any load placed on the resonant system greatly attenuates movement of the piezoelectric disc, which in turn limits the power output of the system. Moreover, the range of frequencies over which such a system performs useful work is very limited. Still further, the use of a piezoelectric disc as the generating element may impose power or space limitations.
The Chapin patent illustrates that piezoelectric elements have been used in conjunction with fluidic circuit devices as sensors in which electrical signals are generated and used to indicate the status of a physical property which the device is designed to monitor. Although not specified in the patent, such uses have also included sensing and measurement by combination of one or more piezoelectric elements with a fluidic oscillator (see, e.g. U.S. Pat. No. 4,930,357 Thurston et al.). However, such combinations are unsuitable as power sources because of their extremely low electrical output.
An objective of this invention is to provide a fluidically-driven generator which does not depend on resonant operation and which produces sufficient electrical power to be suitable for use in control systems for aircraft.